You can use the following built-in functions with list box objects.
Function  | 
Description  | 
bottom [of]  | 
Returns the line number of the last line in the list box.  | 
top [of]  | 
Returns the line number of the first line in the list box (which is always 1).  | 
textual line from  | 
Returns the text that appears on the specified line of the list box. (See textual Object Inquiry Built-in Function in the Reference Guide.)  | 
selected line  | 
Returns the currently selected line in for each selected line loop.  | 
selected line from  | 
Returns the line number of the line that the user has selected from the list box. If used on a multiple-selection list box, it returns only the first line selected.  | 
window yposition of  | 
Returns the line number of the first line displayed in the list box.  |